1. Statement of the Technical Field
The invention relates to optical fibers. More particularly, the invention relates to a filled-core optical fiber spliced to a standard optical transmission fiber and a method of making the same.
2. Background of the Invention
Optical fibers are often used in systems for data transmission applications and sensing applications. These systems require the use and mating of optical fibers extending from various sources. Such sources include data sources and light sources. In such applications, an optical fiber is sometimes used for providing a capillary waveguide. The capillary waveguide could be spliced to a standard optical transmission fiber coupled to a data or light source. The capillary waveguide provides additional capabilities in optical communications and sensing applications as compared to a standard optical fiber device. Such capabilities include filtering capabilities and parameter of interest measuring capabilities.
As should be understood, the capillary waveguide is an optical fiber having a hollow core. The hollow core is filled with a fluid having one or more desired optical properties. For example, the fluid has an index of refraction that varies in accordance with changes in temperature. In an optical fiber having a grating disposed in the cladding region adjacent the hollow core, the wavelengths of light that are able to pass through the core depend on the index of refraction of the fluid. Similarly, the wavelengths of light that are able to be reflected by the core depend on the index of refraction of the fluid. As such, the optical properties of the core can be controlled by selectively varying the temperature of the fluid. In addition, a parameter of interest, such as the temperature of the fluid can be measured by detecting the wavelengths of light that have passed through the core. Likewise, the parameter of interest can be measured by detecting the wavelengths of light that have been reflected by the core.
It should be noted that there is great difficulty associated with splicing opposing ends of a filled-core optical fiber with a standard optical transmission fiber. In this regard, it should be understood that optical fibers have relatively small dimensions and cross-sectional areas. As such, the splicing of two (2) optical fibers is accomplished by precisely aligning their axis so as to minimize losses. The splicing generally involves employing a mechanical splice technique or a fusion splice technique.
The mechanical splice technique generally involves utilizing a mechanical splice to physically hold the ends of the optical fibers together. The mechanical splice provides a means to secure the optical fibers in an axially aligned configuration. Mechanical splices have been found to be effective in maintaining the alignment of the optical fibers. However, the splice resulting from said mechanical splice technique suffers from being less robust than desired and typically has a higher insertion loss than a fusion splice.
The fusion splice technique generally involves aligning opposing ends of an optical fiber with the ends of conventional, solid core optical transmission fiber. Thereafter, the fusion splice technique involves performing actions to melt the adjacent ends of the optical fibers together. The melting can be accomplished utilizing a flame, an electric arc or the like. Despite the advantages of the fusion splicing technique, it suffers from certain drawbacks. For example, the optical fibers are exposed to high temperatures during the fusion splicing technique. The high temperatures can damage the optical properties of a fluid contained within an optical fiber. As such, the types of fluids that can be selected for use in communications and sensing applications are limited.
In view of the foregoing, there remains a need for an improved filled-core optical fiber arrangement and method of making the same that avoids exposing the fluid in the core to high temperatures generated during splicing that could damage the optical properties of the fluid.